


yours and mine

by kinkykawa



Series: youngblood (miyacest one-shots) [5]
Category: Haikyuu!!
Genre: Alpha Miya Osamu, Alpha/Beta/Omega Dynamics, Biting, Breeding Kink, Cunnilingus, Incest, M/M, Omega Miya Atsumu, PIV Sex, Top Miya Osamu, Twincest, bondmark, canonverse
Language: English
Status: Completed
Published: 2020-07-28
Updated: 2020-07-28
Packaged: 2021-03-05 23:33:48
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,826
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25573651
Author URL: https://archiveofourown.org/users/kinkykawa/pseuds/kinkykawa
Summary: Now, they are twenty-one and living in a different city, just the two of them together. Now Osamu has Atsumu in heat, a sweaty whimpering mess on their sheets. The air inside their tiny apartment is heavy with their scents, thick with arousal and adoration. Atsumu always looks gorgeous like this — skin flushed and warm, hair a rumpled mess, lips parted on a whine. Only for Osamu. Always for Osamu.
Relationships: Miya Atsumu/Miya Osamu
Series: youngblood (miyacest one-shots) [5]
Series URL: https://archiveofourown.org/series/1933474
Comments: 12
Kudos: 536





	yours and mine

**Author's Note:**

  * For [DalHnrz](https://archiveofourown.org/users/DalHnrz/gifts).



> written as a request for D, who asked for omegaverse osaatsu with a bondmark! set in canonverse as a sort of omegaverse AU to "fundamentals". tossed in some breeding kink because Why Not XD
> 
>  **content warning:** atsumu is written as an omega with an AFAB body, altho i try to use neutral/non-explicit terms when referring to his body during sex. something to keep in mind before reading!
> 
> edited a little bit but i'll come back and fix anything i spot. enjoy the fic!!

Osamu doesn’t know when he’d started wanting to touch Atsumu.

He’s aware their relationship is extremely skewed, from the perspective of anyone who isn’t the two of them. Siblings and twins grow up together all the time, form strong bonds and close relationships, but he has to wonder, how many of them go through life carrying _you were born for me_ inside their ribs? How many of them look at each other and think, _you were born for me_ and know it’s true?

Because it _is_ true, for the two of them, at least. Osamu looks at Atsumu smirking at him across the classroom and feels the tug in his chest, magnetized like solar wind. An alpha and an omega, with scents matching perfectly — coffee and chocolate, mingling sweet and heady. Osamu thinks about Atsumu and thinks, _you were born for me._

_You are half of me, you are mine._

The first clumsy press of their mouths comes after their first Interhigh.

Atsumu always takes losses hard. He spends days seething in frustration, redoing every faulty play in his head. But he’s rarely like this — teeth bared, shoulders hunched, fists pressed to the cold metal locker; scent bitter and acrid in the air. The rest of the team has already filtered out of the club room, tired and listless. Only Osamu is left to watch the way Atsumu’s shoulders shake.

“‘Tsumu,” he says, and his twin crumples.

“I couldn’t—” he snarls, sinking to the floor. “I couldn’t.”

(He doesn’t complete the sentence, he can’t. Osamu hears him anyway.)

“ _No_ ,” he snaps back, willing his feet to move and carry him over to where half his heart lies in a wreck. “It ain’t just you — don’t be a fuckin’ moron, it wasn’t just you.”

(He cannot do gentle. Not in words, not in most things. Osamu is an alpha not made for soft edges and softer actions. Not that Atsumu has ever needed gentle; omega or no, Atsumu is all sharp edges in his own right. But still. Sometimes Osamu wishes he had more to give.)

“I’m not being a—” Atsumu hiccups. He digs his fingers into the front of his twin’s jacket so hard Osamu worries about the fabric. His scent is distressed, pained, _wrong._ “Fuck you, I’m not—”

“It ain’t just you.” Osamu pries Atsumu’s hands from their death grip; predictably, his twin struggles. Atsumu tries to pull back but Osamu won’t let him. He scents the air desperately, the deep scent of fresh coffee, familiar and soothing. “We didn’t do nothing wrong. We just weren’t the better team.”

Atsumu makes a frustrated, pained noise and Osamu echoes that frustration, because his twin shouldn’t be like this. He wants Atsumu to stop shouldering the result of an entire goddamn tournament on his shoulders. Wants Atsumu to _blame me too, call me out too. Call the rest of us out._

 _Defeats belong to both of us too_ , he thinks, and tugs his brother forward.

The first press of their mouths is less of a kiss and more of a desperation. Osamu’s parted lips catch the corner of Atsumu’s, and they’re both clumsy in their bitterness. But Osamu leans back in, tilting his head and threading fingers through his twin’s sweat-matted hair, and this time he catches Atsumu’s exhale between his teeth.

He kisses Atsumu, half-wild and angry and frustrated. Pushes until Atsumu’s head hits the wall, cradled by Osamu’s practice-worn hands. Deepens the contact, sliding his tongue between Atsumu’s lips. His brother is never more beautiful than when he’s on a volleyball court and this is not the first time Osamu has wanted to kiss him, but it _is_ the first time he finally follows through. And this, like everything else, is just one more touch between them.

Osamu kisses Atsumu because they both hurt, because he can, because Atsumu is here and he wants to.

When Atsumu finally responds, tugging Osamu in by his jacket and biting at his lower lip, it feels like vindication and vindictiveness all at once. His fingers brush against Osamu’s neck, digging in just under the jaw, and Osamu’s whole body throbs with _want._

They sit there, tangled up in each other, until well after they’ve caught their breath, sweat cooled on bruised skin. Little by little, Atsumu’s grip eases and his scent settles. A while later and his head drops to Osamu’s shoulder, tilted so his exhales dust Osamu’s collarbone. His lips brush just under Osamu’s scent gland, making him shiver.

“Fine,” he says, and the teasing lilt of his voice is back; the wryness that Osamu loves, that pisses him off. “S’all yer fault we lost.”

Osamu snorts before he can stop himself, and just like that they’re both laughing. He slumps back to lie on the floor, tugging his twin down with him. And Atsumu in his arms, against his chest, feels like home.

“Fuck you,” he retorts, and Atsumu grins, bright as the sun.

Osamu has no idea if he’d already wanted to touch Atsumu before that, or if that kiss had awoken something inside of him, or if it was just another inevitable development in whatever relationship existed between them. All he knows is that touches have always been free and easy between them, so kissing simply makes sense. And as they kiss — stealing presses of lips in the bathroom in the morning, or on a deserted staircase at school, or in the locker room after training — Osamu has to wonder why they hadn’t done it sooner.

Kissing Atsumu is easy as breathing. Osamu leans in as a tease, as a provocation, as a desire, as a comfort. Atsumu always lifts his face up in answer. They slot together seamlessly, alpha and omega, twin and twin; two people whose sharp and ragged edges just fit.

Every escalation from there feels natural and inexorable. The first time Atsumu gets his hand around Osamu’s cock and Osamu bites a ring of dark red into Atsumu’s shoulder because it’s so good, _so good, ‘Tsumu._ The first time Osamu pins Atsumu down to the mattress and ducks between his thighs, tasting cum and slick, making Atsumu writhe and whine and scent so heavily Osamu is dizzy from cocoa and sweetness. The first time Osamu fucks Atsumu, right before his heat — a thrill and a risk in one, the two of them tucked away in Atsumu’s room, when both their parents were away. Osamu’s mouth on Atsumu’s neck, chocolate and salt; Atsumu’s hands on his skin, callused and holding tight; the way it had felt to sink into each other for the first time, to call each other _mine._

They were born for each other, after all.

And now—

Now, they are twenty-one and living in a different city, just the two of them together. Now Osamu has Atsumu in heat, a sweaty whimpering mess on their sheets. The air inside their tiny apartment is heavy with their scents, thick with arousal and adoration. Atsumu always looks gorgeous like this — skin flushed and warm, hair a rumpled mess, lips parted on a whine. Only for Osamu. Always for Osamu.

“ _Alpha,_ ” he whines, and Osamu is helpless to oblige.

“Needy little thing, aren’tcha,” he teases, mouthing his way up Atsumu’s leg, pausing to lightly bite at the taut skin of a muscled thigh. He nuzzles into the crease between thigh and hip, licks at salt-sweat skin. Atsumu’s scent is overwhelming, drawing him in. Osamu’s grin sharpens as he presses his mouth to slick folds, swiping his tongue up and then sucking. Atsumu cries out, hips jerking sharply; Osamu pins him down, eats him out until he’s a loud, trembling mess. He drags his tongue up Atsumu’s torso, already littered with hickeys and bite marks; sucks harshly at his chest (one day, maybe, god, he wants—). He kisses Atsumu’s neck, the heady pulse of a scent gland, soon, soon, _soon—_

“‘Samu, come _on_ , I need — _fuck me—_ ”

Osamu chuckles breathlessly, wide palms denting strong thighs as he makes Atsumu open up for him. The head of his cock brushes against Atsumu’s entrance, making them both gasp. Osamu buries his face into Atsumu’s shoulder as he thrusts again, and again, over and over until he finally slips inside. He’s fucked Atsumu before but like this — so hot and wet, so _open_ for him, and the _sounds_ Atsumu makes, the way he clutches at Osamu like letting go would kill him—

 _Alpha,_ Atsumu calls him, again. Osamu buries himself to the hilt and bruises his omega’s mouth with a kiss.

“Gonna knot ya,” he pants breathlessly, fucking into Atsumu, a quick snap of his hips. “God, fuck, ‘Tsumu — _so good_ — gonna knot ya, fill ya right up — gonna make you take it—”

Atsumu’s hands bury themselves in his hair as he drags Osamu back down, tilting his head back to bare the long stretch of his neck. Osamu’s head is spinning from the scent of them, the feel of Atsumu under and around him; he inhales in a gasp, pressing an open mouth over the throb of the omega’s pulse. Atsumu’s legs wrap around his waist, pulling him further in, turning his thrusts shallow and sharp. They kiss clumsily, interrupted by hitched breaths and bitten-off profanities and strangled cries. When Atsumu climaxes, it’s with Osamu drinking in the taut arch of his body, the clench of fingers in the pillow overhead; the sweet way he _begs_ for Osamu to “ _knot me_ , alpha — alpha, _‘Samu_ —”

Osamu feels his knot catch against Atsumu’s slick entrance, presses his forehead to Atsumu’s chest with a muffled groan. And when he finally comes, pressed so hard into Atsumu he can feel every tremor through the omega’s body — Osamu turns his head and sinks rut-sharpened teeth into Atsumu’s neck. Bitter chocolate taste floods his mouth as Atsumu tenses underneath him, writhing, clenching around the alpha’s cock.

They come down slowly, panting against skin and refusing to withdraw from the press of their bodies. Every move Osamu makes shifts his cock where they’re still locked together, and he’s come inside Atsumu so much he can feel the slight swell to his stomach. It brings to mind other scenarios, a jumble of thoughts in Osamu’s sex-muddled brain — what if it takes; there’s days yet to Atsumu’s heat; Osamu’s gonna fuck him all through it until he’s a sticky, filthy wreck; the fact that they’re now mated, _bonded._ He feels one of Atsumu’s hands creep between them, brushing lightly over his pelvis, and kisses the slow-blooming smirk off Atsumu’s mouth.

“ _Down,_ omega,” he murmurs, nipping at Atsumu’s lip. There’s a faint, answering happy warmth echoing across their newly-formed bond that sends a thrill through Osamu’s body. He bites harder, tugging at that plush bottom lip before letting go, then ducking down to nuzzle at where the bondmark sits prominently on Atsumu’s neck. And Atsumu laughs, soft and warm and happy, burying his hand in Osamu’s hair to keep him close.

“ _Make me_ , alpha.”

**Author's Note:**

> HOPE Y'ALL LIKED THAT feel free to leave a comment on anon/guest — or find me on twitter [@kinkykawa_](https://twitter.com/kinkykawa_) for more osaatsu and other kinky content XD read the carrd before following!


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